At the construction site, technicians use ultrasonic metal testing equipment to test whether the pipeline welds are defective. The scanner is composed of a frame with magnetic wheels, using a spring to keep the probe in contact with the pipe. The wet zone is an ultrasonic coupling agent, which can transmit sound to the pipeline wall.
In an ultrasonic test with ultrasonic metal testing equipment, the ultrasonic transducer connected to the diagnostic machine will cross the inspected object. As in the immersion test, the transducer is usually separated from the test object by a coupling agent (such as oil) or water. However, when using an electromagnetic acoustic transducer to conduct ultrasonic testing, no coupling agent is required.
1. High penetration, being able to detect the defects deep within the component.
2. High sensitivity, allowing detection of tiny defects. In many circumstances, it only needs to approach one surface.
3. In the aspect of determining the depth of the internal defects and the thickness of components with paralleled surfaces, it has higher accuracy than other non-destructive methods.
4. The ability to estimate the size, direction, shape, and property of the defects.
5. The ability to estimate the alloy structure of components with different acoustics characteristics.
6. It is harmless to the operation or nearby personnel and has no effect on nearby equipment and material.
7. It is capable of conducting portable or highly automatic operations.
There are two approaches to receiving ultrasonic waveforms: reflection and attenuation. In the reflection (or pulse-echo) mode, when the "sound" is reflected back to the device, the transducer conducts the sending and receiving of pulse waves. The reflected ultrasonic waves come from the interface, such as the back wall of the object or the defect inside the object. The diagnostic machine displays these results in the form of signals, whose amplitude represents the intensity of the reflection, and distance represents the arrival time of the reflection. In the attenuation (or straight through) mode, the transmitter sends ultrasonic waves through one surface, and a separate receiver detects the number of ultrasonic waves that reach the other surface after passing through the medium. Defects or other conditions in the space between the transmitter and receiver can reduce the amount of sound transmitted, thereby indicating their presence. The use of a coupling agent improves processing efficiency by reducing the loss of ultrasonic wave energy due to the separation between surfaces.